1. Field of the Invention
The invention relates generally to a filter element, and more particularly to a filter element having a corrugated or embossed composite nonwoven filter media.
2. Discussion of the Prior Art
Some known filter media composite constructs incorporate a wet-laid paper making process to produce the substrate, and an electro-spun technology to deposit a lightweight nanofiber coating on one or both sides of the filter media substrate. Typically the media substrate has a basis weight of 100-120 grams per square meter (g/m2), and the nanofiber layer has a basis weight of 0.5 g/m2 or less.
It is known that a media can have three layers that include a base media, an expanded polytetrafluoroethylene (ePTFE) membrane, and a third layer that is an electrically charged nonwoven meltblown layer. However, the electrically charged nonwoven meltblown layer is known to reduce in performance significantly when exposed to moist environments and the electro-static charge diminishes quickly. This known media has not been approved to meet the strict industry test protocols needed for pulsed Gas Turbine Inlet Filtration.
HEPA media with a wet laid glass based media can be found in static Gas Turbine filtration where it is found to be functionally satisfactory for non-pulsed Gas Turbine Inlet Filtration. The wet laid glass based media may be unsuitable for use in pulsed filtration due to its inherent weak strength properties that cannot withstand the stresses of high pressure pulse air cleaning. The weak strength properties would result in the media being torn apart from itself if used in high pressure pulse air cleaning applications.
Filter media composite constructs may be used to provide for clean air provision to various devices. Such devices may include turbine blades. Typical, known filter media may have a new or clean operating efficiency providing for around 55% of capture of 0.3-0.4 μm particles, at a pressure drop typically greater than 7.0 mm H2O, when tested in accordance with the ASHRAE 52.2-2007 test procedure at the known operating flow rate.
Turning to an example device that contains turbine blades, it is logical to try to maintain the turbine blades clean. Fouling and erosion of turbine blades has been known to decrease power output of turbines and increase the frequency of outages to repair the blades. One current procedure for cleaning turbine blades requires taking the turbine off-line at periodic intervals to water wash the blades clean. Turbine down time may be expensive because the turbine is not operating and therefore, power generation is curtailed. It would be desirable to provide a higher efficiency filter media than the known filter media to reduce or eliminate turbine down time to clean the turbine blades.
The best in performance of current technology is rated per ASHRAE 52.2 at F-9, using standard wet laid base media coated with an electrospun fiber surface layer. To date the maximum efficiencies have been limited by the electrospinning process to around a maximum of 75% efficiency when challenged with 100% 0.30 micron DOP particles. This has been achieved with either heavy layers of elecrospun fibers on one surface of a wet laid base media or the use of a nanofiber layer on both surfaces of the base media.